This invention relates generally to prepress photography and more particularly to an improved method and apparatus for accurately positioning copy which is to be photoreproduced by a step-and-repeat camera.
Prepress photography often involves photo reproduction of a large number of originals which have a common size and shape. For example, book pages are frequently photographed in a step-and-repeat mode in order to produce a large number of copies of the book.
Modern step-and-repeat cameras of the type shown in U.S. Pat. Nos. 3,998,546 and 4,582,406 to Wally are normally used in this type of prepress operation. Such cameras can produce an image of an 8 page film "flat" in about 1 1/2 minutes with every image on the film flat in an accurate position ready for plating. High production rates are essential from an economic standpoint, and it is common practice for successive pages to be photographed every 15 seconds. If the pages are not large or difficult to handle for some other reason, the average interval for filming successive pages can be as low as 10 seconds. Each cycle requires the operator to load a sheet of copy on the subject holder, stand aside during its exposure, retrieve the copy from the subject holder after exposure, stack the copy on other copy sheets, secure the next sheet of copy, and prepare to load it on the subject holder.
In the past, the practice has been to accurately position the original copy on the subject holder through the use of registration pins which project from the holder. The copy is provided with punched holes which are located on the top and bottom margins outside of the part of the copy that is to be photographed. The punched holes are located such that when applied to the registration pins, the copy is accurately located on the subject holder to be photographed by the step-and-repeat camera.
The hole punching operation is carried out ahead of time, usually off-line in an area of the prepress department located near the camera. Typically, a two-headed pneumatic punch is used for punching of the registration holes. An operator slides the copy which is to be punched beneath a film positive that rests on a light box and is fastened to the box along its top edge. The film positive has boundaries which define the edges of the type or other features that inform the operator where the original must be located and how it must be oriented while the holes are punched. After the copy has been properly positioned using the film positive as a guide, a footswitch is triggered to activate the punch.
Because the operator must rely on "eyeballing" for proper location of the copy, considerable care must be exercised by the operator in order to achieve the necessary accuracy. If the operator is careless or lacking in skill, the lines of type can be skewed or the margins can be unduly wide or narrow. Aside from possible inaccuracies, this procedure is characterized by considerable time requirements o the part of relatively highly skilled workers. Punching of the film can actually require almost as much time as the photographic process itself.
It is also noteworthy that a major part of the book printing industry involves duplication of old volumes that are no longer in print. Such volumes may be valuable and/or fragile. In order to film the individual pages, it is necessary to remove the binding so that each page is then loose. If the margins of the pages are narrow, as is often the case, it is not possible for registration holes to be punched due to space limitations. Each page must then be taped or glued to a larger carrier sheet and the carrier sheet must then be punched near its margins. The opposite sides of the pages cannot be photographed without removing the copy sheets from the carrier sheets, reversing them and remounting them on new carrier sheets.
As can easily be appreciated, this procedure is highly labor intensive. In addition, the fragile pages of old volumes often cannot withstand as much handling as this requires without being damaged or even destroyed.
Accordingly, it is evident that there is a need to eliminate the necessity for copy to be punched in order to provide the potential for drastically cutting both labor cost and production time.